Efficient and Stable Graded CsPbI_3−xBr_x Perovskite Solar Cells and Submodules by Orthogonal Processable Spray Coating

Solution-processed CsPbI₂Br thin films often suffer from poor film properties, which are indictive of electronic defects that can lead to poor stability. In addition, significant efforts are required to reduce the large cell-to-module performance gap for inorganic perovskite PV devices. Here, we report the fabrication of inorganic CsPbI₂Br-based perovskite thin films with a well-defined CsPbI_3−xBr_x composition gradient by a scalable, orthogonal processable spray-coating approach. The graded structure broadens the absorption wavelength range, increases carrier lifetime, and facilitates charge separation and collection. With this approach, we demonstrated a monolithically integrated perovskite submodule based on the graded CsPbI_3−xBr_x by spray coating with an efficiency of 13.82% (112-cm² aperture area) and ∼9% degradation over 1,000-h continuous 1-sun light soaking.